Tying device in which the drive means are electric servomotors

ABSTRACT

Apparatus for tying objects with wire is disclosed including a feeder for feeding and tightening the wire around the object, the feeder being driven by an electric servomotor which can be rotated through a predetermined number of revolutions for feeding and tightening the wire, an adjustable guide rail for guiding the wire around the object and for tightening the wire when the guide rail is opened, a locking unit for locking the wire around the object, a wire twister for twisting the wire into a knot, the wire twister being driven by an electric servomotor so that it can be rotated through a predetermined number of revolutions for twisting the wire into a knot, and a wire cutter for cutting the wire after the knot has been formed.

FIELD OF THE INVENTION

The present invention relates to a device for tying objects with wire,for example bales of fiber material.

BACKGROUND OF THE INVENTION

Pulp bales can either be individually tied into bales, or this can bedone in the form of stacked units comprising a certain number of bales,normally six or eight. Such a unit load will generally have a weight ofbetween one and two tons. The strength of the wire connection which isused to bind together the unit load, therefore, is very important fromthe point of view of safety, particularly since several persons canstand close to the load when it is being lifted by means of such wires.The equipment used for twisting the knot in a tied loop, as well as theknot itself, therefore, is subject to very comprehensive safetyregulations and accurate safety control.

The tying device generally comprises a unit for feeding the wire throughan openable wire guide rail around the object. The feed unit is alsoused for tightening the wire. A twisting member is also generallyutilized, which comprises a unit for locking the end of the wire, a unitfor twisting a wire knot, a cutting unit, and a unit for pushing out theknot.

The wire guide rail extends about the object to be tied and guides thewire while it is being fed. The wire is then fed through the twistingmember about the object to be tied. When the free end of the wire thusarrives at the twisting member for the second time, the wire is stoppedand retained in the locking unit, whereafter it is tightened byreversing the feed unit. The wire guide rail is thus opened after thewire has been fed around the object, and the wire is then drawn aroundthe object to be tied, the knot is twisted, the wire is cut and pushedout of the twisting member.

These various units are normally driven and controlled hydraulically bymotors and cylinders. It has been found, however, that this drive systemfails to work with the desired degree of precision during the tyingprocess. Ample margins are, therefore, required to ensure its properfunctioning, especially during the wire feeding, wire tightening andtwisting steps. This also implies that the wire can be subjected to suchstresses during tying, that the wire must be designed thicker than wouldbe required for merely holding the tied objects together. The hydraulicmotors, furthermore, require relatively complicated and bulky hydraulicassemblies, which creates the risk of functional disorder and highservice costs.

SUMMARY OF THE INVENTION

According to the present invention, these and other objects have nowbeen achieved by the invention of apparatus for tying objects with wirehaving an end which comprises feed means for feeding and tightening thewire around the object, feed drive means for driving the feed means, thefeed drive means comprising a first electric servomotor, whereby thefirst electric servomotor can be rotated through a first predeterminednumber of revolutions for feeding and tightening the wire around theobject, a guide rail adjustable between opened and closed conditions forguiding the wire around the object, whereby the guide rail can guide thewire around the object when in its closed condition and the wire can betightened around the object when the guide rail is in its openedcondition, locking means for locking the wire around the object afterthe end of the wire has been fed entirely around the object, wiretwisting means for twisting the end of the wire into a knot, wiretwisting drive means for driving the wire twisting means, the wiretwisting drive means comprising a second electric servomotor whereby thesecond electric servomotor can be rotated through a second predeterminednumber of revolutions for twisting the end of the wire into a knot, andwire cutting means for cutting the wire after the knot has been formed.

In accordance with one embodiment of the apparatus of the presentinvention, the apparatus includes wire indicator means for indicatingthe position of the end of the wire proximate to the locking means.

In accordance with another embodiment of the apparatus of the presentinvention, the apparatus includes ejecting means for ejecting the knotfrom the apparatus. Preferably, the apparatus also includes pneumaticactuator means for actuating the guide rail and the ejecting means.

In accordance with another embodiment of the apparatus of the presentinvention, the apparatus includes pneumatic actuator means for actuatingthe guide rail.

In accordance with another embodiment of the apparatus of the presentinvention, the apparatus includes combined pneumatic and hydraulicactuating means for actuating the locking means and the wire cuttingmeans.

In accordance with another embodiment of the apparatus of the presentinvention, the apparatus includes a plurality of transmitters positionedaround the object for indicating the position of the wire whereby theapparatus can be operated based thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully appreciated with reference tothe following detailed description, which, in turn, refers to thedrawings in which:

FIG. 1 is a side elevational, partially schematic view of a tyingapparatus in accordance with the present invention;

FIG. 2 is a top perspective, partially cutaway view of a wire twistingmeans for use in connection with the apparatus of the present invention;and

FIG. 3 is a schematic representation of a pneumatic and/or hydraulicsystem for use in controlling the various elements of the apparatus ofthe present invention.

DETAILED DESCRIPTION

The tying device of the present invention is of the general type shownand described in Swedish Patent No. SE 380,496 (see U.S. Pat. No.3,929,063. Referring to the drawings, in which like reference numeralsrefer to like elements thereof, the tying device hereof comprises astand 10, on which the different units are arranged. A feed unit 11feeds tying wire 12 from a wire magazine around the object to be tied 13and thereafter tightens the wire. A wire guide rail 14 extends about theobject 13. A twisting member 15 comprises a guide rail 16 for guidingthe wire through the twisting member 15, a unit 17 for locking the endof the wire, a unit 18 for twisting a wire knot, a unit 19 for cuttingthe wire, and a unit 20 for pushing out the finished twisted knot.

The entire tying device is preferably movable so that it can be placedin a conveying track for the objects to be tied, and can be easilyreplaced when required.

The feed unit 11 comprises a guide wheel 21, about which the wire 12runs, and a driven feed wheel 22, to which at least one counter-pressureroll 23 abuts. The feed wheel 22 is driven by first electric servomotor24.

The wire guide rail 14 is openable and provided with grooves for thewire 12. During feeding of the wire, the rail 14 is held in closedposition, preferably by means of pneumatic piston/cylinder units 40.During tightening of the wire, the wire guide rail 14 is opened by thepiston/cylinder units 40.

The tying member 15 is exchangeable, and is detachably attached to thedrive means for the units 16-20 of the tying member. The drive means arespringloaded single-acting piston/cylinder units 25-28, which actuatethe guide rail 16, locking unit 17, cutting unit 19 and push-out unit20, as well as a second electric servomotor 29, which actuates thetwisting roll 31 of the twisting unit 18 by means of pinions 30.

The piston/cylinder units 25 and 28, which actuate the guide rail 16 andpush-out unit 20 are preferably included in a pneumatic system, whilethe piston/cylinder units 26 and 27, which actuate the units 17 and 19for locking and cutting, are preferably included in a combinedpneumatic/hydraulic system. In this combined system the piston/cylinderunits 26 and 27 are directly actuated hydraulically from a pneumaticallyactuated power amplifying hydraulic cylinder 32. In this manner, thehydraulic system is minimized while at the same time power and safetyare maintained.

During the feeding of the wire, the feed unit 11 is driven by the firstelectric servomotor 24 through a predetermined number of revolutions, sothat a definite wire length is fed around the object 13 and the wire endarrives at the locking unit 17. The length of the wire feed 12 iscounted from the wire end passing an indicator 33 located at thein-feed. The wire end is retained in the locking unit 17.

The wire is thereafter tightened by reversing the servomotor 24 of thefeed unit 11 until the wire has been tightened down onto the object 13,and the necessary torque in the servomotor 24 has been obtained.

After the predetermined torque for wire tightening has been achieved andbeen maintained for a short time, the second electric servomotor 29 isactivated for driving the twisting roll 31 of the twisting unit 18.Rotation of the servomotor 29 is controlled so that the twisting roll 31is first rotated through a predetermined number of revolutions and anadditional angle and thereafter is reversed through the same angle. Inthis manner, a certain over-twisting is obtained, which compensates forthe spring back of the wire knot.

When the twisting step is completed, the wire is cut in the cutting unit19, and the push-out unit 20 ensures that the knot leaves the tyingmember 15.

After it has been cut, the wire is pulled back by the feed unit 11 pastthe indicator 13, and the device is ready for a new tying operating.

By using electric servomotors for driving the feed unit and the twistingunit, it is possible to accurately control the wire feed, wiretightening and twisting steps. The number of revolutions and the angularposition of the servomotors can be indicated, for example, by pulsemetering or in some other way. Speed, acceleration and retardation ofthe servomotors can be controlled so that jerks and jolts in the wireare avoided. It has thus been found possible according to the presentinvention to reduce the wire diameter while maintaining functionalsafety, compared with conventional equipment, for example from 2.3 mm to2 mm.

In addition to the indication equipment mentioned above, transmitters 50can be positioned at different locations for indicating the position ofthe wire and movable parts of the different units. Such an arrangementcan be utilized advantageously, for example, for functional informationand trouble shooting.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

I claim:
 1. Apparatus for tying objects with wire having an endcomprising feed means for feeding and tightening said wire around saidobject, feed drive means for driving said feed means, said feed drivemeans comprising a first electric servomotor whereby said first electricservomotor can be rotated through a predetermined number of revolutionsfor feeding said wire around said object and can be counter-rotatedthrough a predetermined number of revolutions for tightening said wirearound said object, a guide rail adjustable between opened and closedconditions for guiding said wire around said object whereby said guiderail can guide said wire around said object when in said closedcondition and said wire can be tightened around said object when saidguide rail is in said opened condition, locking means for locking saidwire around said object after said end of said wire has been fedentirely around said object, wire twisting means for twisting said endof said wire into a knot, wire twisting drive means for driving saidwire twisting means, said wire twisting drive means comprising a secondelectric servomotor whereby said second electric servomotor can berotated through a predetermined number of revolutions for twisting saidend of said wire into said knot, and wire cutting means for cutting saidwire after said knot has been formed.
 2. The apparatus of claim 1including wire indicator means for indicating the position of said endof said wire proximate to said locking means.
 3. The apparatus of claim1 including ejecting means for ejecting said knot from said apparatus.4. The apparatus of claim 3 including pneumatic actuator means foractuating said guide rail and said ejecting means.
 5. The apparatus ofclaim 1 including pneumatic actuator means for actuating said guiderail.
 6. The apparatus of claim 1 including combined pneumatic andhydraulic actuator means for actuating said locking means and said wirecutting means.
 7. Apparatus for tying objects with wire having an endcomprising feed means for feeding and tightening said wire around saidobject, feed drive means for driving said feed means, said feed drivemeans comprising a first electric servomotor whereby said first electricservomotor can be rotated through a predetermined number of revolutionsfor feeding said wire around said object and can be counter-rotatedthrough a predetermined number of revolutions for tightening said wirearound said object, a guide rail adjustable between opened and closedconditions for guiding said wire around said object whereby said guiderail can guide said wire around said object when in said closedcondition and said wire can be tightened around said object when saidguide rail is in said opened condition, locking means for locking saidwire around said object after said end of said wire has been fedentirely around said object, wire twisting means for twisting said endof said wire into a knot, wire twisting drive means for driving saidwire twisting means, said wire twisting drive means comprising a secondelectric servomotor whereby said second electric servomotor can berotated through a predetermined number of revolutions for twisting saidend of said wire into said knot, wire cutting means for cutting saidwire after said knot has been formed, and wire indicator means forsensing said end of said wire proximate said feed drive means todetermine a position of said end of said wire proximate to said lockingmeans.
 8. The apparatus of claim 7 including ejecting means for ejectingsaid knot from said apparatus.
 9. The apparatus of claim 8 includingpneumatic actuator means for actuating said guide rail and said ejectingmeans.
 10. The apparatus of clam 7 including pneumatic acutuator meansfor actuating said guide rail.
 11. The apparatus of claim 7 includingcombined pneumatic and hydraulic means for actuating said locking meansand said wire cutting means.
 12. Apparatus for tying objects with wirehaving an end comprising feed means for feeding and tightening said wirearound said object, feed drive means for driving said feed means, saidfeed drive means comprising a first electric servomotor whereby saidfirst electric servomotor can be rotated through a predetermined numberof revolutions for feeding said wire around said object and can becounter-rotated through a predetermined number of revolutions fortightening said wire around said object, a guide rail adjustable betweenopened and closed conditions for guiding said wire around said objectwhereby said guide rail can guide said wire around said object when insaid closed condition and said wire can be tightening around said objectwhen said rail is in said opened condition, locking means for lockingsaid wire around said object after said end of said wire has been fedentirely around said object, wire twisting means for twisting said endof said wire into a knot, wire twisting drive means for driving saidwire twisting means, said wire twisting drive means comprising a secondelectric servomotor whereby said second electric servomotor can berotated through a predetermined number of revolutions for twisting saidof said wire into said knot, wire cutting means for cutting said wireafter said knot has been formed, and a plurality of transmitterspositioned around said object for identifying the position of said wirewhereby said apparatus can be operated based thereon.
 13. The apparatusof claim 12 including wire indicator means for indicating the positionof said end of said wire proximate to said locking means.
 14. Theapparatus of claim 12 including ejecting means for ejecting said knotfrom said apparatus.
 15. The apparatus of claim 14 including pneumaticactuator means for actuating said guide rail and said ejecting means.16. The apparatus of claim 12 including pneumatic actuator means foractuating said guide rail.
 17. The apparatus of claim 12 includingcombined pneumatic and hydraulic actuator means for actuating saidlocking means and said wire cutting means.